White light-emitting materials have long been sought for energy-efficient lighting and advanced display technologies. A new study by researchers at Universitat Jaume I de Castellón and Gunma University demonstrates that such materials can be made transparent, flexible, and efficient by carefully engineering the polymer network — a web of long-chain molecules that forms the material’s structure — surrounding the light-emitting dyes.

“Rather than emphasizing the advantages of organic emitters, I would argue that the real advantage lies in the generated polymers, which are both transparent and flexible — properties that are uncommon in the field of white-light emission,” Professor Francisco Galindo of Universitat Jaume I de Castellón, one of the authors of the study, said in an email.

What white light-emitting films are and why they matter

White-light emission is the ability of a material to shine across the full visible spectrum, producing light similar to sunlight. It underpins technologies such as display backlighting, flat lighting panels, and energy-saving, solid-state lamps. “Potential applications for any material exhibiting white-light emission lie in the fields of lighting and display technologies,” Galindo explains.

Researchers have explored many strategies to achieve this effect, but most existing white-light emitting systems take the form of powders, thick coatings, or brittle fragments. While these demonstrate that white-light emission is possible, they are difficult to integrate into real devices and often require additional processing.

The new study took a different approach. By embedding light-emitting dyes within a carefully designed polymer matrix, the researchers aimed to create films that are thin, transparent, and flexible, unlike rigid powders or coatings.

Overcoming challenges in creating white light-emitting films

Such films could be directly laminated onto display panels or used in lightweight lighting modules, but producing them posed significant challenges. White-light emission typically requires blending multiple dyes, each producing a different color, yet incorporating these dyes into solid materials often reduces their brightness or stability.

The researchers had to carefully control how the dyes interacted with the polymer host to preserve both their efficiency and the desired optical properties — a challenge they successfully tackled through precise material design and experimentation.

“The materials we study are made using a heat-driven chemical process that creates highly reactive molecules,” Galindo explains. “These conditions can easily damage the light-emitting dyes. A significant part of this work involved finding the right conditions to keep the dyes intact throughout the entire process.”

Traditionally, researchers have tried to fine-tune the dyes to achieve the right color balance. Galindo and colleagues, however, asked whether adjusting the chemical environment of the dyes could unlock white light emission without changing the dyes at all; their solution was to shift the focus from the dyes to the surrounding host material. This “matrix-driven” or “non-dye-centric” strategy puts the emphasis on the polymer structure rather than the molecular design of the dyes themselves.

A ‘matrix-driven’ approach to white-light emitting devices

“Most of the previous research leading to white-light-emitting systems has been based on solution-phase studies, in which two or three dyes are dissolved in a solvent and the photophysical behavior of the system is investigated,” Galindo explains. “More recently, the field has progressed toward incorporating these dyes into solid supports, making the systems more suitable for technological applications.”

Many studies have used inorganic supports such as porous silica. Galindo’s group instead turned to a family of acrylic polymers known as PHEMA, which they had previously explored for uses ranging from biosensing to cancer therapies. Into this polymer, they embedded two carefully chosen dyes, one blue-emitting and one yellow-emitting.

Initially, the films did not produce white light. “The intuitive approach would have been to modify the dyes — adjusting parameters to promote or suppress energy transfer processes,” Galindo notes. “However, we chose a different path: rather than altering the dyes, we asked whether changing the makeup of the polymer mixture — essentially adjusting how water-attracting and water-repelling components are balanced — could influence the outcome.”

By systematically varying the composition of the polymer, the team identified a formulation that produced stable white light with high efficiency. The films converted incoming energy into visible light with a quantum yield of 0.51 — meaning that just over half of the energy absorbed by the material was re-emitted as light — and reached color coordinates very close to the ideal white point used in lighting technology.

Straightforward transition to lighting, displays, and beyond

Although the study is still fundamental research, its implications are promising. Flexible, transparent white-light films could serve as coatings for display panels, lightweight alternatives to current lighting solutions, or components of wearable devices. “Given the advantages of the materials — namely, their flexibility and transparency — such a transition is expected to be relatively straightforward,” Galindo says, contrasting this approach with most reported solid-state systems that come as powders or brittle fragments.

The researchers see their “non-dye-centric” strategy as broadly applicable wherever dyes are used. “Carefully modifying the polymer matrix — without significantly altering the embedded dye — is highly general and can be applied across a broad range of light-based technologies,” Galindo explains.

His group is particularly interested in medical and sensing applications, including photodynamic therapy, antimicrobial and anticancer systems, and wearable biosensors. In these contexts, the dye is often fixed, so optimizing the surrounding polymer offers greater control over performance.

With a vast array of acrylic components to experiment with, this approach provides considerable flexibility. “This strategy offers considerable freedom in tuning the properties of the resulting material to meet specific functional requirements,” Galindo says. By demonstrating that the polymer environment can be as decisive as the dyes themselves, the study opens a new perspective in designing light-emitting films that are versatile, durable, and efficient.

Reference: Jean C. Neto et al., Organic, Transparent, and Flexible Films Exhibiting White-Light Emission via Polymer-Network Engineering: A Non-Dye-Centric Strategy, Advanced Optical Materials (2025). DOI: 10.1002/adom.202501380.

Feature image credit: Paco Silva (Clandestino) via Pixabay